WBC-VIII-Vol.4 – Resources – Forestry, Plantations and ... - BambuSC

identification, apparent unsuitability of the species for the area, and the fact that this species was only planted in
Kakamega, the species is not included in this analysis. Another case is that of Dendrocalamus. asper. The
relatively good performance of this species under cultivation in Nairobi suggests that this species may be
interesting for plantations. D. asper was planted in the Muguga trials but the species was not identified at the
site, so no data was recorded for analysis. It is possible that D. asper was mixed up with D. brandisii. In
Kakamega, a clump resembling D. asper was observed in the plot of D. brandisii. D. asper was however not
originally included in the Kakamega trial site. Some elements of doubt therefore remain in the analyses and
taxonomical clarifications are required.
Methodology
The method of analyzing the sites involved the following steps:
1) Observations were made on various clumps of each species and the number of culms and new shoots per clump
was counted or estimated. In very dense clumps it was not possible to count the number of culms and therefore an
estimate of the number of culms was made based on the number of culms counted for a particular area of the
clump. Based on the counted and/or estimated number of culms of the sampled clumps of each species, average
numbers of culms per clump per species was calculated.
2) The observation of the clumps involved visually identifying small, medium, and large culms and measuring the
circumference of selected samples using a measuring tape. Based on the measured samples of various sizes of
culms of each species, and taking into account the fact bamboo culms are tapered from the base towards the tip of
the culm, an average culm diameter was calculated for each species.
3) The average height of the culms of each species was determined in many cases, roughly by observation, as well as
accurately, by felling culms and measuring their precise length in meters. This method was applied by sampling
culms in several clumps and an average height per species was calculated.
4) The wall thickness of the bamboo culms was calculated based on published information (as well as on unpublished
information collected by the author over the years) regarding the ratio of wall thickness to culm diameter per
species.
5) The dry weight of culms was calculated of the basis of the solid volume of the bamboo culm, using the specific
gravity of bamboo to determine the mass. In calculating the volume of the culms, radial shrinkage of the culms is
taken into account. Shrinkage ranges from 4-14% in the wall thickness and 3-12% in diameter. (Liese, 1985.)
Culm shrinkage varies from species to species and depends very much on the moisture content of the culm at the
time of harvesting. As a working assumption, the mean radial shrinkage factor of 9% in the wall thickness and
7.5% in diameter for tropical bamboos was assumed. The specific gravity of bamboo ranges from 0.5 to 0.8 (0.9)
g/cm³ (Liese, 1985). The value of 0.65 was taken as a working assumption for all species, which is the
approximate value for most species of the Bambusa and Dendrocalamus genera. The mass to volume ratio of air
dried bamboo with 11% moisture is about 0.7 g/m³ and this was used as a working assumption for determining air
dry weight of culms. The solid volume of bamboo is determined by multiplying the length of the culm by the solid
cross section area of the culm. The solid cross section area is calculated by subtracting the culm cavity cross
section area from the total cross section area. The cross section areas are calculated using the formula for the area
of a circle (Area = Πr²). Once the solid volume of the culm is estimated, the mass can be determined by means of
the mass to volume ratio of bamboo. The method is purely mathematical but provides a rough estimation of culm
weight. The actual average weight of the culms may vary by +/-20%. Clearly, the most accurate way of
VIII World Bamboo Congress Proceedings Vol 4-119